1. Field of the Invention
The present application relates to the field of thermoelectric power generation, and more particularly to systems for improving the generation of power from thermoelectrics where the heat source varies in temperature and heat flux.
2. Description of the Related Art
Thermoelectrics are solid state devices that operate to become cold on one side and hot on the other side when electrical current passes through. They can also generate power by maintaining a temperature differential across the thermoelectric. Under many operating conditions, however, thermoelectric power generators are exposed to a combination of changing heat fluxes, hot side heat source temperatures, cold side heat rejection temperatures, and other variable conditions. In addition, the device properties, such as TE thermal conductance, Figure of Merit Z, heat exchanger performance all have a range of manufacturing tolerances that combine to, in general, reduce device performance. As a result, performance varies and operation at a predetermined set point can lead to performance degradation compared to design values.
Any process that consumes energy that is not 100% efficient generates waste energy, usually in the form of heat. For example, internal combustion engines generate a substantial amount of waste heat. In order to improve the efficiency of the internal combustion engine; such as in automobiles, various ways to capture some of this waste heat and convert it to a useful form have been considered. Placing thermoelectrics on the exhaust system of an automobile has been contemplated (See U.S. Pat. No. 6,986,247 entitled Thermoelectric Catalytic Power Generator with Preheat). However, because the exhaust system varies greatly in heat and heat flux, providing a system that is effective has been illusive. By way of example, compared to optimal performance, degradation in automobile waste heat recovery system performance can be very significant, amounting to at least 30%.